Electronic balancing and follower circuits



Aug. 1, 1950 E. L. GINZTON 2,516,365

ELECTRONIC BALANCING AND FOLLOWER cmcums Original Filed March 15, 1943 33 Hl-lill 32 a4 INVENTOR Eon/n20 L. G/NzTo/v BY Patented Aug. 1, 1950 .11., UNITED STATES PATENT OFFICE- v v v FOLLOWER Edward L. fiinzton, Garden City, N. assignor to The Sperry Corporation, acorporation of Delaware "Ifhisi'nvention relates generally to electronic balancing and follower circuits, and the present application is a division of copendi'ng application Serial No. 509,867, filed November ll, j l943, 1now Patent No. 2,485,584, issuedpctober 25, 1949, in the same of Edward L. Gifizton, which is in turn a division of application Serial No. 479.294, filed March 15, 1943, now abandoned. D

An object of the invention is to provide electropic circuits for producin a current proportional in magnitude and corresponding in directicn, to the polarity and magnitude oi a control voltage, without placing anylload upon the control voltage. I

Another object is to provide improved circuits for prb'ducing an output voltage signal whichcorresponds in magnitude but is reversed inpolarity with respect to an input or control signal.

Other objectsand advantagesrwill become apparent "from the specification, taken connection with the accompanying drawings wherein the invention is embodied in concrete form. I

In the drawings, l t t Fig. 1' is a 'w'i'rir'ig" diagram of an electronic cir: cult which maybe employed for various useful purposes in a computing system; and

Fig. 2 is a wiringdiagram of a more accurate electronic circuit for accomplishing one of the functions of the circuit shown-in Fig. 1.

Referring now toti g. 1, thereis shown a circuit useful in' various waysrdr' operating on voltage signals in a computing system. As shown, an electron tube indicated as atriode, isprovi'ded', having its grid 22; connected to the pngrdunded lead I oi." leads I and supplying a directvolt'age input signal '(V1). The cathode 2Q of tube 3B is connectedito the groundedlead 2' throu'ghresistors 3| and 32. The point 33; intermed'iate' resistors: 3| and His connected through the variable resistor 34to the negative side of the plate supply voltage' shbwdas battery 35. Batter is is shown grounded at a point ifite'rmediate its; positiveand negative terlhinals. The plate tinf of tube 3b is" connected to the positive side or the plate supply batter 'through the resister 36. A closed circuit is formed'jac'ross' the terminals of battery 35' through the [resistors 36; 31. and 38, the last of which is variable. due outputlead 39 is connected toa point ll intermediate the resistors 37 and 38. The" other output lead-40 isconnected to'the point 33'. A grounded output lead 42 may also tensed, i fdesired;

The electron circuit: through the tube may be considered as" "traveling from. ground through resistbrsfl and 3|, through tubest and resistor 36 12 Claims, (Cl; its-171) toj'the positive side of battery 35, and then back to fgro'und. Another closed circuit is formed from groundthrough the resistor 32 and variable resistor 34 to the negative side of battery 35 and then to ground.

With zero voltage signal (V1) applied to the grid 28 of tube 301, that is, with the quiescent value of current flowing through the tube, variable resistor 34 is adjusted until the point 33 and output conductor 40 are at ground potential. At the same time, variable resistor 38 is adjusted until the point 4i and output conductor 39 are at ground potential.

flf a positive voltage signal (Vi) should be recived, it will be apparent that because of the increase of current flow through resistor 36 the potential ofpoint 43 will decrease. Accordingly, the potential of point M and that of the output conductor 3'9 will decrease to a negative potential proportional to the input voltage signal (V1). At the same time, due to the increase of current flow through resistor 32, the potential of point 33 and that of the output conductor 40 Will increase in the positive direction by a corresponding amount. Similarly, should a negative voltage signal be received, a proportional positive signal will. be produced on output lead 39 and a proportional neg-.

ative signal will beproduced on lead 40.

Moreover, due to an increase of current flow through resistors 32 and 3| resulting from a positive input signal impressed upon the grid, the cathode of tube 30 will become more positive, causing the r d to become more negative with respe t to the cathode. This will tend to decrease thac'u'rrent flow through the tube, thus opposing the eifect of the received signal. In this way, inversePf'eedback; is provided which stabilizes the ratio of output to. input voltage signals by elimiiiatifig the effects of changes in the tube characteristics caused by age of the tube, variations in external conditions,; such as temperature and humidity', and other reasons.

fllhe circuit shown in Fig. l may therefore be used, for three different purposes. It may be used as. a. ffollower circuit in which an output voltage signal-is provided across output condutors Hand 52, which is of the same polarity and proportional to the inputsignal (V1). Such a follcwer circuit may be employed in order to producean output voltage signal from'which current] may be: drawn, said output voltage signal being proportional to an input voltage signal from which itis not desired to draw current. The circuitshown in Fig. l-may also be employed as a reversing circuit wherein an output voltage tional to the input signal, one being of the same" polarity and the other being of the opposite polarity to that of the input signal.

If a more accurate follower circuit than that shown in Fig. 1 is desired, recourse may be had to the circuit shown in Fig. 2. As there shown,

two electron tubes ill, 'H are provided. The grid 68 of tube It is connected by lead I to the ungrounded side of the input signal (Vi), whereas the grid 69 of tube TI is connected'to the plate It of tube I through the resistor 12.

cathode ill of tube H3 is connected to ground through the biasing resistor 13, whereas the cathode ll of tube H is connected to ground through the biasing resistor 14, the inverse feed-back resistor 1'5 and input voltage lead 8. The ungrounded side of the input signal is connected to the point '56 intermediate resistors 14 and 15,

through the resistor 11.

'The positive side of the plate supply battery '58 i directly connected to the plates '10 and H of tubes lo and H through resistors 19 and 80, respectively. As shown, battery 18 is connected to ground at a point intermediate its positive and i negative terminals. Its negative terminal is connected to the plate of tube 10 through variable resistor 8i and resistor T2. The negative terminal is also connected to the plate of tube ll through the resistors 82 and 83, the first of which is variable. The output voltage signal appearing on conductor 84 is obtained from a point 85 intermediate resistors 82 and 83. Another variable resistor 8%? is provided, one end of which is connected to the negative terminal of battery 18 and the other end of which is connected to the point 16.

With the quiescent value of tube current flowing, that is, with zero input signal (Vi), resistors cause an increase in potential of the cathode of tube 10. Accordingly, the grid of tube will become less positive with respect to the cathode, thereby tending to decrease the current flow in the tube and opposing the increase caused by the positive input signal. Similarly, as the current flow through tube H decreases as a result of a positive input voltage signal (as previously explained) the potential drop through the resistors "I4 and '15 will also decrease, causing the cathode of tube H to become less positive. The grid of tube H is thereby caused to become more positive with respect to the cathode, causing an increase in current flow through tube H, which tends to oppose the decrease in current flow caused by the positive voltage input signal. By employing inverse feedback in this way, in both stages of the circuit, the output voltage signal is rendered almost completely independent of changes in the tube characteristics, and dependent only on the input voltage signal (Vi). If desired, the circuit of Fig; 2 could also be used as a reversing circuit or a "balancing circuit by also extracting the potential of point I6.

Although direct current voltage signals have been employed throughout for the purpose of illustration, it will be apparent that many of the principles embodied in the present" invention could obviously be employed to operate in a similar manner on alternate current voltage signals. It is therefore to beunderstood the'present' invention is not intended to be limited to the use of direct current voltage signals only.

Since many changes could be made in the above construction and many apparently widely dilferent embodiments of this invention could be 8|, 82 and 86 are all adjusted so that the points sistor 8!) will cause a corresponding increase in the potential of the plate of tube H, and consequently of point 85 and of output lead 84. Should a negative input voltage signal be received, an exactly opposite sequence of the events will occur, causing a corresponding negative voltage signal to appear on output lead 84. Thus, the output signal produced will always be proportional to, and of the same polarity as, the input signal received.

The advantage of this follower circuit lies in the increased amount of inverse feedback obtained by employing two stages. Inverse feedback is obtained in the circuit of tube 10 through the biasing resistor 13. As the current through tube 18 increases due to a positive voltage signal, the

increased potential drop through the resistor will made without departing from the scope thereof, it is intended that all matter contained in the, above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. V

-What is claimed is:

1. An electronic follower circuit for producing a loadable output signal voltage proportional to a non-loadable input signal voltage, comprising an electron tube having a control grid adapted to be connectedto receive one side of said input signal voltage, a plate supply voltage source for said tube, a pair of resistors connected so as to be interposed between the cathode of said tube and the other side of said input signal voltage, a third resistor'interposed between a point intermediate said pair of resistors and the negative side of said:

said intermediate point and said other side of said input signal'voltage' to be zero when said input voltage is zero, and means for extracting the voltage between said intermediate point and said other side of said input signal voltage as:

the output signal voltage.

2, An electronic followercircuit for producing a a loadable output signal voltage proportional to f a non-loadable input signal voltage, comprising a first and'second electron tube having plate and cathode circuits, the control grid of the first of said tubes being arranged to be energizedwith said input voltage, a common plate supply voltage source for said tubes, said source having an-interm'ediatepoint grounded, two closed resistive circuits also energized from said source, acornmon resistor in thefirst of said circuits and in the plate circuit of said first tube, a second common resistor in the second of said circuits and, in the plate circuit of said second tube, means for ad-} justing one point ,ineach pt. said, resistive circuits waive zero sna s whenssiuiin ut voltage is zero, means for energizing the control grid ,otsaid second tube from tbvol'tageoisaid,point in said first resistive circuit, and means .torextracting the voltage of said point in said .second resistive circuit as the output voltage;

3. An electronicffollower circuit, as claimed in claim '2, further including inverse {feed-back resistor in. the cathode circuits. of leach or i said tubes. I i

I i. An electronic follower circuit forproducinsa loadable output signal voltage proportional to a non-loadable input. signal voltage, comprising first-ans second electron 'tubes having plate and cathode circuits, the dirst ofysaid tubes having a control grid arranged to be connected so as to be energizedwithsaid input "signal voltage, .a common plate supply voltage source "for said tubes, two closed electrical circuits also energized from said source, the first of said electrical circuits including an impedance elementi-in common with the platecircuit' of said first-tube, and means for causing the voltage between a point in ssaid first circuit and one side of said input voltage to be zero when said input voltage is zero, said second electrical circuit including animpedance-element in cornmon with the plate circuit 0f said second tube, and means 'forcausing thevoltage betwcen apointinsaid second circuit and said point in said first circuit to be zerowhensaid input voltage ,is .zero,.the second of said-tubeshavingacontrol 1. grid connected to said pointin said firstciredit, and means for extracting the voitagewbetween'said point in said second circuit and the other side of said input voltage, as the output signal voltage.

5. An electronic follower circuit, as claimed in claim 4, further including an inverse feed-back impedance element in the cathode circuits of said tubes.

6. An electronic reversing circuit for supplying an output signal voltage proportional but of opposite polarity to a received input signal voltage, comprising an electron tube having a control grid arranged to be energized with said received voltage, a plate supply voltage source for said tube, said source having an intermediate point grounded, a closed resistive circuit energized from said source, a common resistor in said resistive circuit and in the plate circuit of said tube, means for adjusting the voltage of a point in said resistive circuit to have zero voltage when said received voltage is zero, means for extracting the voltage of said point, and a pair of resistors connected in series with each other between the cathode of said tube and ground, and a further resistor connected from the junction between said pair of resistors to the negative terminal of said plate supply voltage source.

7. An electronic reversing circuit for supplying an output signal voltage proportional but of opposite sense to a received input signal voltage, comprising an electron tube having a control grid arranged to be energized with said input voltage, a late supply voltage source for said tube, a closed electrical circuit energized from said source, a common impedance element in said electrical circuit and in the plate circuit of said tube, means in said electrical circuit for causing the voltage between a point in said electrical circuit and one side of said input signal voltage to be zero when said input signal voltage is zero, and means for extracting the voltage between said point and said one side of said input signal voltage as the outputsignal voltage, and a pair of re;- sistors connected in series with each other between the 30213110118011 said tube [and ground, and a further resistor .connectedirom the junction between said pair of resistors to the negative terminalof said plate supply voltage source.

l i 8. An electronic reversing circuit tor supplying an output signal voltageproportionalbut of opposite polarity to a received :input signal voltage, comprising an electrontube having a control grid arranged to be energizedfrom one side of the source of input signal voltage, a platesupply voltage .source for said tube, a closed resistive circuit energized from said plate supply source, said resistive circuit including a resistive element connected between the positive side of .said source and the plateof saidtubeand means for causing the .voltage. between a point in said resistive cir cuit and one side of said input signal voltage source to ,be zero when said input voltage is zero, and means extracting the voltage betweenisaid point and said one side .of :said input voltage source as the output signal voltage, and a pair of resistors connected .inlserieswith each other between the cathode =of said tube and groundand .a furtherresistor connected from the junction between said pair of resistors to the negative terminal of said plate supply voltage source.

"9. An electronicreversing circuit for supplying an output signal voltage proportional but of oppoe site polarity to a received input signal voltage, comprisingan electron tube having .a control grid arranged tolbe energized with said input voltage, a plate supply voltage source-tor :said tube, a closed resistive circuit energized from said source, said resistive circuit including a resistive element connected between the positive side of said source and the plate of said tube and means for causing the voltage between a point in said resistive circuit and one side of said input voltage to be zero when said input voltage is zero, means for extracting the voltage between said point and said one side of said input voltage as the output signal voltage, inverse feed-back means including a pair of resistors connected in series with each other between the cathode of said tube and ground, and a further resistor connected from the junction between said pair of resistors to the negative terminal of said plate supply voltage source.

10. An electronic balancing circuit for supplying two output signal voltages above and below ground respectively by an amount proportional to a received input signal voltage, comprising an electron tube having a control grid arranged to be energized with said received voltage, a plate supply voltage source for said tube, said source having an intermediate point grounded, two closed resistive circuits energized from said source, the first of said circuits being connected between the extreme positive and negative terminals of said source, and including a resistor in common with the plate circuit of said tube, and the second of said circuits being connected between said intermediate point and the negative terminal of said source, and including a resistor in common with the cathode circuit of said tube, means for adjusting a point in the first of said resistive circuits to have zero voltage when said input voltage is zero, means for adjusting a point in the second of said circuits to also have zero voltage when said input voltage is zero, and means for extracting the voltage of each of said points.

11. An electronicbalancing circuit for supply.

ing two output signal voltages of opposite polarity both proportional to an input signal voltage comprising an electron tube having its grid arranged to be energized with said input voltage, a plate supply voltage source for said tube, two closed resistive circuits energized from said source, the first of said circuits including being connected between the extreme positive and negative terminals of said source and a resistive element in common with the plate circuit of said tube, and the second of said circuits being connected between said intermediate point and the negative terminal of said source, and including a resistive element in common with the cathode circuit of said tube, means in each of said circuits for causing the respective voltages between one side of said input voltage and respective points in said circuits to be zero when said input voltage is zero, and means for extracting the respective voltages between said one side of said input voltage and said respective points as the respective output signal voltages.

12. An electronic balancing circuit for supplying two output signal voltages of opposite polarity both proportional to an input signal voltage, comprising an electron tube having its grid arranged to be energized with said input voltage, a plate supply voltage source for said tube, two closed resistive circuits energized from said source, the first of said circuits being connected between the extreme positive and negative terminals of said source, and including a resistive element in common with the plate circuit of said tube, and the second of said circuits being connected between said intermediate'.v point and the negative terminal of said source and including a resistive element in common with the cathode circuit of said tube, means in each of said circuits for causing' the respective voltages between one side of said input voltage and respective points in said circuits to be zero when said input voltage is zero, means for extracting the respective voltages between said one side, of said input voltage and said respective points as the respective output signal voltages, a further resistor connected between the cathode of said tube and said point in said second of said resistive circuits;

EDWARD L. GINZTON.

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